The present invention relates to refrigeration systems or the like, and more particularly, to a refrigeration system employing evaporative subcooling to provide for increased efficiency and metered overflow of cooling water to prevent mineral build-up on the cooling coils.
Evaporative heat exchangers are well known in the cooling art. Especially in desert areas where the humidity is low, evaporative coolers have long been used as a primary, or secondary cooling means. In essence, water is sprayed into a chamber or over a coil so that the surrounding ambient air or the fluid in the coil is cooled. The cooling is highly efficient since the latent heat of evaporation of the water droplets is substantially more effective to absorb heat than the surface cooling effect of water or air alone can be.
There has been at least one effort to apply an evaporative condenser or cooler to a refrigeration system, more specifically to an air conditioning system. This concept is set forth in the U.S. Pat. No. to Beasley et al. 4,404,814, issued Sep. 20, 1983. In this particular system, the evaporative cooler is used as a de-superheater for the very specific purpose of reducing the compressor discharge pressure and the refrigerant temperature entering the condenser. The de-superheater is energized only in the event that the compressor pressure/temperature exceeds an upper threshold level. In the Beasley arrangement, the temperature of the liquid refrigerant entering the condenser is reduced at the high end of the temperature scale. This arrangement unfortunately ignores the fact that reducing the temperature at the high end of the scale is not efficient since the ambient air passing over the condenser coils can do this job more effectively for a given amount of power input.
In addition to providing an approach of de-superheating, there have been some efforts in the prior art to use auxiliary cooling devices as subcoolers. In this effort for example, additional heat exchange coils are provided in the closed loop refrigeration system downstream of the condenser. This art includes attempts at providing subcooling units of the counterflow heat exchanger type as an add-on or retrofit for existing refrigeration systems or the like. A typical system utilizing a simple liquid cooling coil is shown in the U.S. Pat. No. to Jennings 3,177,929, issued Apr. 13, 1965. While these units have been around for years, it is generally accepted that they have not been successful because the increase in efficiency of the subcooling unit working alone does not justify the cost of the unit. It has been felt by many in the industry that if the efficiency of the subcooling unit could be improved, the cost would clearly be justified. However, prior to the present invention no such advance has been made.
Subcooling the liquid refrigerant on the downstream or liquid side of the condenser thus holds promise if the increase in efficiency is improved to make it economically feasible. The effect of this subcooling can be visualized on the standard pressure/enthalpy chart for the standard CFC refrigerant. The cooling capacity of the refrigerant is increased as represented by the increased area on the left side within the diagram lines of the chart. The saturated liquid refrigerant is cooled beyond the reference line on the left side providing an increase in efficiency.
Accordingly, additional effort is justified in seeking new ways of subcooling other than through a simple liquid/liquid counterflow heat exchanger. While such counterflow heat exchangers are useful, used alone they have simply proven not be of great enough efficiency to become a wide-spread commercial reality. It is thus appropriate to look for a new approach to subcooling in a refrigeration system using more efficient approaches, singularly or in combination.